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Is "Wilkes" marked on the lockplate, or on the bbl ?
Unless you can discern & clearly picture some bbl and/or lockplate markings/stamps, your guess is as good as mine.
If you can measure the bore, it might also be of some help.
IIRC, "Wilkes" was an English (London) lock-maker, who most likely supplied gunlocks to whomever.
IMO, that piece looks like it was either assembled from parts, and/or cut down from a military issue, for use as a foraging gun (to shoot small game for food, during a military campaign).
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